River Flood Warning 43, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
302 PM CDT WED MAR 17 2010

.DISCUSSION...
LOW CLOUDS CONTINUE TO ERODE OVER PORTIONS OF OUR EAST THIS
AFTERNOON...AND A PRETTY UNEVENTFUL NIGHT IS IN STORE ACROSS THE
AREA. THINKING FOG IS LESS LIKELY TONIGHT UNDER A SOUTH TO
SOUTHWESTERLY LOW LEVEL FLOW...BEFORE WINDS SWITCH TO THE
WEST/NORTHWEST IN OUR EXTREME WEST TOWARD 12Z AS A WEAK COLD FRONT
BEGINS TO PUSH INTO THE CWA. OUT AHEAD OF THIS FEATURE...WILL SEE AN
INCREASE IN HIGH/MID CLOUDS THROUGH THE NIGHT. WITH THE SOUTHERLY
INFLUENCE OUT AHEAD OF THE FRONT OVERNIGHT LOWS WILL BE MILD FOR
THIS TIME OF YEAR...GENERALLY IN THE LOWER 30S.  /JM

THURSDAY STILL LOOKING MILD AS WINDS TURN FROM THE SOUTHWEST AND
WEST TO THE NORTHWEST. THE ONLY FLY IN THE OINTMENT FOR A REALLY
NICE MIXING DAY WILL BE SOME RESIDUAL SNOW COVER IN SW MN AND A
STEADY INCREASE IN MID AND UPPER LEVEL MOISTURE. REGARDLESS...LOOKS
LIKE MOST SPOTS WILL CREEP UP TO AROUND 50...WHILE NEAR THE MO RIVER
UPPER 50S WILL BE POSSIBLE.

THE BIG CHANGE HEADING INTO THURSDAY NIGHT AND FRIDAY IS THE
STRENGTH AND PLACEMENT OF THE NORTHERN STREAM JET MAX. TODAYS RUNS
HAVE COME IN STRONGER AND FARTHER SOUTH WHICH WOULD INDICATE THAT
THE MID LEVEL BOUNDARY SHOULD DROP FARTHER SOUTH THAN PREVIOUSLY
EXPECTED...SO PRECIPITATION AMOUNTS ALSO LIKELY TO BE LIGHTER.
DECREASED QPF AMOUNTS MOST LOCATIONS...KEEPING ABOUT A THIRD TO A
HALF AN INCH FROM SUX TO SLB. SO...THE CHANCE FOR AN ADVISORY TYPE
SYSTEM IS ALSO LOWER...BUT ADVISORY TYPE SNOW WILL LIKELY ONLY BE A
FEW COUNTIES TO THE SOUTH SO ANY CHANGE IN MOVEMENT OF THIS SYSTEM
TO THE NORTH WOULD BRING A THREAT TO THE FAR SOUTHERN COUNTIES.
THURSDAY NIGHT INTO FRIDAY MORNING WILL SEE MOST OF THE
PRECIPITATION THAT DEVELOPS COME ALONG SOMETHING CLOSE TO THE 700MB
FRONT AND FALL MAINLY AS RAIN. EXPECT A FAIRLY QUICK TRANSITION TO
SNOW THOUGH...SO STILL A THREAT FOR 2 TO 3 INCHES OF SNOW FROM THE
MISSOURI RIVER VALLEY INTO NORTHWEST IOWA. FAIRLY MILD LOWS ON
THURSDAY NIGHT IN MAINLY THE MID 30S...BUT LITTLE DIURNAL RISE
FRIDAY WITH CLOUDS AND PRECIPITATION EXPECTED...SO HIGHS FRIDAY
MAINLY IN THE 30S.

FRIDAY NIGHT INTO SATURDAY WILL SEE A CONTINUED SURGE OF COLDER AIR
IN THE LOW LEVELS AS PRECIPITATION SHIFTS SOUTH OF THE CWA. WILL
LEAVE IN SOME HIGHER EVENING POPS IN NW IA...BUT REMOVE SNOW THREAT
FOR SATURDAY. SHOULD BE BREEZY AS WELL WITH THE COLDER AIR ADVECTING
IN...LOWS IN THE 20S AND HIGHS IN THE 30S

IN THE LATTER PERIODS(SUN/WED)...A STRONG NORTHWEST FLOW ALOFT WILL
TRANSITION TO A FLAT RIDGE ALOFT TOWARDS THE END OF THE PERIOD.
OVERALL...CHANCES FOR PRECIPITATION NOT THAT GREAT...BUT STILL LOOKS
LIKE THE POTENTIAL FOR A LITTLE WARM AIR ADVECTION PRECIPITATION
TUESDAY INTO WEDNESDAY WITH SOME OBVIOUS DISCREPANCIES THAT FAR OUT.
WILL CONTINUE SOME LOW POPS TO COVER THIS. AS FOR
TEMPERATURES...LOOKING LIKE BELOW NORMAL THROUGH THE PERIOD BUT
OVERALL QUITE A BIT OF DISAGREEMENT DURING THIS TIME FRAME. A COUPLE
OF RUNS WANT TO REALLY POUR IN SOME WARM AIR BUT THE ENSEMBLE DATA
NOT SUPPORTING THIS WITH THE MEN HINTING AT COLDER TEMPERATURES WITH
RESPECT TO THE MEX WHICH IS ALREADY COLDER THAN CLIMATOLOGY. SO
PRETTY MUCH AIMING FOR HIGHS IN THE 40S AND LOWS FROM THE UPPER
TEENS TO UPPER 20S. /08

&&

.AVIATION...
GENERALLY VFR CONDITIONS EXPECTED ACROSS THE AREA TONIGHT. THINKING
THAT REDUCED VISIBILITIES IN FOG ARE LESS LIKELY TONIGHT WITH A
DRIER SOUTH TO SOUTHWESTERLY COMPONENT TO THE WINDS. WINDS WILL TURN
FROM THE NORTHWEST AROUND KHON AFTER 09Z TONIGHT AS A WEAK FRONTAL
SYSTEM PUSHES INTO THE AREA. /JM

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&